Abstract
Glomerular clearance (GC), tubular reabsorption (TR) of albumin and the relatioship between TR and tubular load of albumin were assessed in 108 patients with NIDDM without proteinuria (I; AER≤15, II; 15-49.9, III; 50.0-199.9μg/min) and in 31 healthy controls to clarify the relative contribution of GC and TR to AER. GC and TR of albumin were determined by inhibiting TR of albumin using L-arginine infusion.
In controls and NIDDM-I, AER was significantly correlated with GC of albumin, while no correlation existed between them in NIDDM-II and III. No significant difference in GC of albumin was found in relation to the degree of microalbuminuria. On the other hand, AER in 3 groups of NIDDM increased in close relation with deterioration of TR of albumin. Furthermore, when TR of albumin was plotted against the tubular load of albumin, there was a linear relationship between them in all subject groups. The regression lines in controls and NIDDM-I were quite similar, while within the tested range of tubular load, the capacity of TR deteriorated in relation to the advance of microalbuminuria.
These results indicate that in a state of normal AER, TR as well as GC of albumin determine AER, and that the reduced TR of albumin plays a causal role in the development of microalbuminuria in NIDDM.
